This invention relates generally to the field of network addressing, and more particularly to a method and system for processing fragments and their out-of-order delivery during address translation.
Due to the success of the Internet, the Internet Protocol (IP) has become the primary networking protocol. Major concerns of the Internet community are the depletion of global IP address space (IPV4) and the complexity of configuring hosts with global IP addresses for Internet access. To extend the life of current IP address space and provide configureless access, network address translation (NAT) and its extension, port address translation (PAT), have been employed.
Network address translation supports connectivity between the Internet and hosts using private addressing schemes. This connectivity provides configureless access to the Internet in that hosts may have independently assigned, globally non-unique addresses that need not be coordinated with the Internet Address Numbering Association (IANA) or other Internet registry. Network address translation pairs up the private addresses to public addresses so that the inside IP addresses appear as legally registered IP addresses on the Internet.
Port address translation allows a number of private network addresses and their ports to be translated to a single network address and its ports. Thus, multiple hosts in a private network may simultaneously access the Internet using a single legally registered IP address. The registered IP address is typically assigned to a router that translates addressing information contained in message headers between the addressing schemes.
Port address translation uses transport layer header information (protocol, port, etc.) to uniquely translate and direct IP traffic to the correct receiver. IP fragments, other than the first fragment, however, do not carry any transport layer protocol information. Thus, when IP fragments are delivered out-of-order, which is common with IP traffic, the IP fragments cannot be translated unless the first fragment of the packet is already received. As a result, the fragments are discarded and the data must be resent. This leads to delays in obtaining information and increased traffic on the Internet.
The present invention provides a method and system for translating addressing information for packetized fragments that substantially eliminate or reduce disadvantages and problems associated with previously developed systems and methods. In particular, the present invention stores fragments delivered out-of-order until additional fragments are received having address translation information with which the stored fragments may be translated.
In accordance with one embodiment of the present invention, a set of packetized fragments in which only a portion of the fragments carry translation information for the set of fragments is translated by storing in a memory fragments received before the translation information. In response to receiving the translation information, the fragments stored in the memory are translated based on the translation information. After receipt of the translation information, fragments are translated as they are received based on the translation information.
More particularly, in accordance with a particular embodiment of the present information, the translation information is address translation information and each fragment is translated by translating addressing information for the fragment. In this embodiment, the fragments may be Internet Protocol (IP) fragments in which only the first fragment carries the translation information. Address translation is performed in accordance with Network Address Translation (NAT) and Port Address Translation (PAT).
The technical advantages of the present invention include providing a method and system for processing fragments during address translation. In addition, it also provides a method and system for processing fragments delivered out-of-order. In particular, fragments delivered out-of-order without address translation information are stored until the address translation information is received. At that time, addressing information for the stored fragments is translated and the fragments are directed to that address. Accordingly, out-of-order fragments need not be discarded nor retransmitted. Thus, any delay is minimized and network traffic reduced.
Another technical advantage of the present invention extends network and port address translation capabilities to forward IP traffic without compromise. This capability makes network and port address translation highly deployable and useful. Moreover, resource impact is minimized by creating fragment-context and searching only when needed. Requirements for dynamic memory objects are also kept to a minimum by using aging timers for both fragment-context and stored fragments.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, description, and claims.